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Making the Best of a Slimy Catch

Millions of giant jellyfish invading the Sea of Japan have beleaguered coastal communities in recent years. Now, researchers have come up with a way to turn their gelatinous carcasses into something useful: a protein that could be added to food, cosmetics, and drugs.

At 2 meters across and weighing 200 kilograms, the hefty Nemopilema nomurai has broken fishing nets and poisoned fish that make it into the haul. Another major nuisance, the smaller moon jellyfish (Aurelia aurita), has blocked the cooling system intake at a power plant and has turned beaches into graveyards as it washes up with the tide. Theories abound for the population explosions. Ideas include harbor construction that created surface space for juveniles, nutrients from agricultural runoff that the jellyfish can feed on, and ocean warming that may boost living conditions. Another possibility is that overfishing of predators allows millions of jellyfish larvae to survive into adulthood.

Their sheer numbers have forced fishermen to give up on chopping them up and throwing them back to sea. Efforts to find a use for them have so far resulted in a baking powder for cookies and crunchy snacks made of dried and salted pieces of jellyfish. But there may be another destination for their slimy bodies. Researchers have found the creatures easily yield oodles of a potentially valuable kind of mucin, proteins that are a main ingredient of saliva and mucus.

The mucin was discovered by accident. A team led by biochemist Kiminori Ushida at the Institute of Physical and Chemical Research (RIKEN) in Saitama, Japan, had turned to jellyfish in their search for a complex sugar in skin and many tissues. Instead, they found a mucin that they dubbed qniumucin (from the Japanese "kuniumu," meaning "rebirth of a country" for the attempt to turn the blobby hordes into a national resource). Its tendency to form a gel might make it useful as an emulsifier in food or a moisturizer in cosmetics, Ushida says, and it could be used as a substitute for gastric juices in people with certain digestive diseases. Qniumucin could also replace cow-derived gastric mucins used in medicines that were taken off the market because of worries about bovine spongiform encephalopathy, mad cow disease.

The researchers say they can extract up to 60 grams of qniumucin from each giant jellyfish; moreover, the structure is similar across five jellyfish species, the team reports online in Journal of Natural Products.

Tests will have to show that qniumucin doesn't provoke an immune reaction before it can be used medically, cautions mucin biologist Tony Corfield of the University of Bristol, U.K. But the study could offer new insights into the evolution of proteins, Corfield says. "We don't know how we arrived at the mucin structures we have in higher mammals." By comparing jellyfish and mammalian versions, researchers may get a better handle on which structures make mucins useful.